Avoid recursive config watches under proot

[jamesx0416]

What Changed

• Use a proot-specific config-directory watcher for keybindings and server settings.
• Keep the existing Effect FileSystem.watch behavior outside proot.
• Under proot, use non-recursive node:fs.watch and emit update events for changed config filenames.

Why

Effect recursive directory watching expands into hundreds of fs_event handles under proot for the T3 userdata config directory. On Android/proot this adds avoidable event-loop and native watcher pressure for two config files that only need shallow directory watching.

This keeps live reload behavior for keybindings.json and settings.json while avoiding recursive watcher fanout when PROOT_L2S_DIR is present.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (not applicable; no UI changes)
• I included a video for animation/interaction changes (not applicable; no UI changes)

Validation: pnpm --filter t3 typecheck

Note

Avoid recursive config watches in proot environments

• Adds a watchConfigDirectory helper in keybindings.ts and serverSettings.ts that selects a watch implementation based on the PROOT_L2S_DIR environment variable.
• When PROOT_L2S_DIR is set, uses Node's fs.watch directly (wrapped in Stream.callback) instead of the Effect FileSystem.watch, avoiding recursive watch issues under proot.
• When PROOT_L2S_DIR is not set, delegates to the existing fs.watch Effect implementation with no behavior change.

^{Macroscope summarized fc93ae1.}